Experimental Study of Micro-Scale Taylor Vortices Within a Co-Axial Mixed-Flow Blood Pump

Taylor vortices in a miniature mixed-flow rotodynamic blood pump were investigated using micro-scale particle image velocimetry (-PIV) and a tracer particle visualization technique. The pump featured a cylindrical rotor (14.9mm diameter) within a cylindrical bore, having a radial clearance of 500m and operated at rotational speeds varying from 1000 to 12000 rpm. Corresponding Taylor numbers were 700-101800, respectively. The critical Taylor number was observed to be highly dependent on the ratio of axial to circumferential velocity, increasing from 1200 to 18000 corresponding to Rossby numbers from 0 to 0.175. This demonstrated a dramatic stabilizing effect of the axial flow. The size of Taylor vortices was also found to be inversely related to Rossby number. It is concluded that Taylor vortices can enhance the mixing in the annular gap and decrease the dwell time of blood cells in the high-shear-rate region, which has the potential to decrease hemolysis and platelet activation within the blood pump.